Relief and topography are often used interchangeably, both referring to the shape and configuration of the land surface. However, topography specifically addresses variations in land elevation on a broader scale.
According to FAO Guidelines from 1990, there are several categories to designate different types of topography based on the slopes of the land surface:
On flat or nearly flat areas, most of the rainwater that falls percolates through the soil. Soils formed under such conditions are representative of the regional climate. They have well-defined soil layers (horizons) and a normal soil profile. However, flat lands with minimal slopes often experience drainage issues due to poor water movement.
Soils on steep slopes are typically shallow, contain rocks, and have less distinct soil horizons. This is because rapid erosion removes surface materials before they can fully develop. Reduced water percolation occurs due to surface runoff, leading to insufficient water for plant growth, which in turn hampers erosion control and soil formation.
Depression areas in semi-arid and sub-humid regions retain more moisture compared to flat terrains. This is due to additional water received as runoff. These conditions, found in areas like the Tarai region of Uttar Pradesh, support more vegetation growth and slower decomposition of organic matter. Consequently, this leads to the formation of darker soils rich in organic material, known as Mollisols.
Topography influences soil formation by impacting temperature and plant growth through slope exposures or aspects. Southern exposures, facing the sun, experience higher temperatures and greater temperature and moisture fluctuations. Northern exposures, on the other hand, are cooler and more humid. Eastern and western exposures fall in between these two extremes in terms of temperature and moisture characteristics.
The active soil forming factors provide the energy needed for soil formation. These factors are primarily climate and vegetation (biosphere).
Climate is the most influential factor that determines the type and speed of soil formation.
Different dominant climates are recognized, including:
Climate plays a dual role in soil formation, both directly and indirectly.
Two key climatic factors, precipitation, and temperature, have the most significant influence on soil formation.
Precipitation
Precipitation is the most significant climatic factor in soil formation. When rainwater percolates through the parent material, it transports various substances in both dissolved and suspended forms. These substances are either redeposited in different areas of the material or eliminated from it as water moves upwards due to surface evaporation, carrying the soluble substances along. Consequently, rainfall leads to the redistribution of both soluble and suspended substances within the soil.
Temperature
Temperature serves as another climatic factor that influences the soil formation process.
For instance, Jenney (1941) found that weathering processes in tropical regions advance three times more rapidly than in temperate areas and nine times faster than in arctic regions.
Organism
Vegetation
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